roles/samba-dc: Fix typo in host principal name

The service principal name added to `/etc/krb5.keytab` had a trailing
`}` character because of a typo in the Ansible task. This resulted in
GSSAPI authentication failing because server processes could not find
the host key in the key table.

roles/samba-dc/tasks/main.yml

@@ -89,5 +89,5 @@
 - name: ensure host keytab exists
   command: >-
     samba-tool domain exportkeytab /etc/krb5.keytab
-    --principal=host/{{ ansible_fqdn }}}
+    --principal=host/{{ ansible_fqdn }}
     creates=/etc/krb5.keytab